The invention relates to a process for thermal treatment of a plastically moldable workpiece, in which the workpiece is plastically molded at a first temperature, is mechanically restrained in this shape by form-fitting and is brought to a second temperature and at least partially subjected to a thermal treatment, whereafter the workpiece is removed. The invention further relates to a device for such thermal treatment.
Thermal treatment is understood to be a treatment by means of the influence of heat and/or cold, in which a workpiece is subjected to temperatures for a certain length of time in order to influence the properties of said workpiece.
It is known to subject workpieces to heat treatment in order to influence certain properties of the workpiece. Workpieces with a simple configuration are clamped during the heat treatment by devices adapted for form-fitting such that the general shape of the workpiece does not change substantially during the heat treatment. However, the thermally induced changes in volume of the workpiece must not be prevented. The disadvantage of said device adapted for form-fitting is in that the contours of the workpiece must be incorporated in the clamping device. With a complex profile this is sometimes impossible or almost impossible or the costs involved are unreasonably high.
Attempts have already been made to restrain workpieces wherein they are embedded in setting, cross-linking or hardening materials such as, for example, plaster. The removal of the workpiece after heat treatment is very disadvantageous in this case, however, as apart from the considerable soiling caused when plaster is knocked off, there is the danger of distortion and damage to the workpiece. The time required for embedding and removal is also disadvantageous. As a rule new embedding material must be used each time embedding takes place.
Heating also causes difficulties with conventional heat treatment processes and devices, manifest in particular in inexact temperature control. This applies to both heating of the workpiece in a furnace and to resistance heating.
The object of the invention is therefore to provide the process and the device for heat treatment of a plastically moldable workpiece of the type described in the introduction, in order to be able, at a reasonable cost, to continuously surround, in a form-fitting manner, workpieces with a more complex configuration, in particular filigree workpieces, over the whole of their profile or surface, or alternatively over parts of their surface, in order to clamp them.